Needle electrodes are designed for use in neurologic examinations using monitoring equipment, namely EMG monitoring equipment. The needle electrodes are connected to monitoring equipment and then inserted into a patient's muscle at the location that is to be stimulated or probed. As a needle electrode is inserted into a patient's body, both the needle electrode and the operator may be exposed to bodily fluids carrying infectious diseases. Because of the danger associated with exposure to bodily fluids, the Food and Drug Administration (FDA) has stringent requirements regarding packaging, sterilization, reuse, disposal and testing performed using needle electrodes.
FDA requirements have resulted in two types of needle electrodes being used in the marketplace. The first type of needle electrode generally used is a disposable needle electrode assembly including a needle electrode, lead wires, and electrical connectors all joined to form a single unit. The needle electrode assemblies are generally sterilized and prepackaged for a one-time use by a physician. The physician opens the sterilized package, connects the needle electrode assembly to the appropriate monitoring equipment, and inserts the needle electrode into a patient's muscle. After completing testing, the entire needle electrode assembly is disconnected from the monitoring equipment and discarded.
Disposable needle electrode assemblies are expensive and highly wasteful of resources due to their one-time use. Disposable needle electrode assemblies also add to the quantity of medical waste produced, increasing waste disposal costs. Because disposable needle electrode assemblies are prepackaged for a specific use, i.e., specific needle size, length, etc., a hospital must stock large numbers of needle electrode assemblies having different sizes and lengths, adding to inventory overhead and storage costs.
The second type of needle electrode assembly commonly used is a reusable needle electrode assembly designed to be sterilized after each use. Similar to disposable needle electrode assemblies, reusable needle electrode assemblies are generally manufactured as a single piece unit including electrical connectors, leads, and needle electrode. Reusable needle electrode assemblies are not as wasteful of resources; however, they are expensive and time-consuming to use due to the complex procedures necessary to sterilize the needle electrode assemblies prior to each use. As with disposable needle electrode assemblies, reusable needle electrode assemblies are generally manufactured as a single unit having a needle electrode of a specific size and length, thus requiring a hospital to stock a wide variety of needle electrode assemblies.
In order to reduce some of the disadvantages of prior needle electrode assemblies, applicant invented a reusable needle electrode assembly that can releasably engage and hold needle electrodes of various configurations. See U.S. Pat. No. 5,482,038 filed concurrently and titled "Needle Electrode Holder." (Attorney docket number CADL-1-7440). To prevent applicant's new needle electrode holder from contacting a patient's skin and thus possibly a patient's bodily fluids during use, a needle electrode configuration that prevents the needle electrode holder from contacting a patient's body or fluids is desired. Preventing the needle electrode holder from coming into contact with a patient's body and bodily fluids eliminates the need to sterilize the holder, decreasing the time and costs associated with using the needle electrode holder. As will be better understood from the following description, the present invention provides a needle electrode configuration that is designed to prevent a needle electrode holder from contacting a patient's bodily fluids.
In electromyographic examinations, it is important that the distal end of the needle electrode be placed within the patient's muscle at the proper position. In the past, physicians have used trial and error to insert a needle electrode into the patient's body to the desired depth. Once inserted, it is common for a patient to move, which often causes the needle electrode to move deeper into the patient's muscle, beyond the desired depth. As will be better understood from the following description, the present invention provides needle electrodes configured in a way that regulates the depth of insertion of the distal end of the electrode into the patient and prevents the needle electrode from moving further into the patient during testing.